According to HowStuffWorks, using lemon juice serves as an alternative for skin lightening that's affordable and not as harsh as acid peels and bleaching agents. The natural bleaching effect of lemon juice has been used as a long-time household remedy for lightening freckles and age spots.
HowStuffWorks explains that placing lemon slices or lemon juice on darkened areas of the skin can lighten them. Frequent application of the lemon juice throughout the day provides best results. Skin irritation or allergic reactions can occur when applying lemon juice on the skin, and significant results may require repeated applications over a long period of time.